Add Public and Internal URLs on your SharePoint server for your Host-Header-Based Hosts

Host-header-based proxy rules require the following alternate access mappings on your SharePoint central administration server:

Set the public URL for the zone to the URL of your virtual host associated with the web application.
Set the internal URL to the server to which the requests from the virtual host are forwarded.

The following table describes an example of the alternate access mappings for host-header-based proxy rules:

Internal URL	Zone	Public URL for Zone
http://www.sharepointserver1.example.com	Default	http://sharepoint.example.com

Open your SharePoint central administration site.
Click Application Management.
Under Web Applications, click Configure Alternate Access Mappings.
Use the examples in the previous table as a guide to edit your public URLs and Add Internal URLs.